Screw compressor with muffle structure and rotor seat thereof

ABSTRACT

A rotor seat for a screw compressor with a muffle structure is provided. The rotor seat includes a seat body, a radial exhaust port arranged at the seat, a female rotor hole and a male rotor hole. The rotor seat further includes a plurality of axial blind holes arranged on a surface where the radial exhaust port is located.

BACKGROUND

The application generally relates to a compressor muffle structure. Theapplication relates more specifically to a rotor seat for a screwcompressor with a muffle structure.

The working principle of compressors commonly used in cooling systems isto increase the pressure of a refrigerant gas from an evaporator to thepressure of the refrigerant gas in a condenser, so that under theincreased pressure, the utilization of the refrigerant can be maximizedto cool a medium to be cooled. In such compressor systems, a screwcompressor can be a commonly used type of compressor. The screwcompressor can be provided with a female rotor and a male rotor (alsocalled a concave rotor and a convex rotor), which rotate in acompression cavity. When the rotors rotate, the suction portcorresponding to the compression chamber is closed, and as the volume ofthe chamber decreases, a gas compression effect is achieved.

A pair of female and male rotors in the screw compressor can incurstrong fluid dynamic noise during high-speed rotation. The noise mainlyincludes periodic gas suction and exhaust noise, expansion and backflownoise of the over-compressed and under-compressed gas, and vortex noisein the tooth slot primitive volume. The fluid dynamic noise is alwaysthe main noise source of a screw compressor and a corresponding coolingsystem. Noise control targeting the fluid dynamic noise can be the mosteffective type but also has long been a technical problem to be solvedin the art.

In order to solve the problem of the exhaust noise, U.S. Pat. No.5,051,077 entitled “SCREW COMPRESSOR” proposes to form different stepsat a radial exhaust port under female and male rotor holes on a rotorseat body, so as to attenuate the exhaust noise. A drawback of thispatent is that only when the volume ratio of the slots formed at theexhaust port reaches a certain value can noise attenuation beaccomplished. However, the formation of the slots reduces the design VI(volume ratio or volume index) of the compressor, thereby deterioratingthe performance of the compressor at designed working conditions.

Therefore, what is needed is a solution which can effectively reduce theexhaust noise and suppress the exhaust noise energy at the sourcewithout deteriorating compressor performance.

SUMMARY

The present invention is directed to a rotor seat for a screw compressorwith a muffle structure. The rotor seat includes a seat body, a radialexhaust port arranged at the seat body, a female rotor hole and a malerotor hole and a plurality of axial blind holes arranged on an arcsurface where the radial exhaust port is located.

The present invention is also directed to a screw compressor with amuffle structure. The screw compressor includes a suction port, anexhaust port, and an operation cavity in communication with the suctionport and the exhaust port. The screw compressor also includes female andmale rotors arranged inside the operation cavity and a rotor seat toreceive the female and male rotors. The rotor seat includes a seat body,a radial exhaust port arranged at the seat body, a female rotor hole anda male rotor hole and a plurality of axial blind holes arranged on asurface where the radial exhaust port is located.

The present application provides a rotor seat for a screw compressorwith a muffle structure. The rotor seat includes a seat body, a radialexhaust port arranged at the seat, and a female rotor hole and a malerotor hole. The rotor seat further includes a plurality of axial blindholes arranged on a surface where the radial exhaust port is located. Inone embodiment, the axis of the blind hole is the normal line, at thehole, of the arc surface where the radial exhaust port is located. Inanother embodiment, the depths of the blind holes are in the range of¼λ±15% of an interested sound frequency or an odd multiple of ¼λ±15% ofthe interested sound frequency, where λ is the wavelength of theinterested sound frequency. In yet another embodiment, the diameters Dof the blind holes are D≦0.586×c/f, where f is the interested soundfrequency, and c is the sound speed in a medium. In still anotherembodiment, the blind holes are distributed in a uniform or non-uniformmanner on the surface where the radial exhaust port is located. In afurther embodiment, the quantity of the blind holes is at least two.

The present application further provides a screw compressor with amuffle structure. The screw compressor includes a suction port, anexhaust port, an operation cavity in communication with the suction portand the exhaust port, and female and male rotors arranged inside theoperation cavity. The screw compressor further includes a rotor seat asdescribed above for receiving the female and male rotors.

The muffle structure formed by the blind holes according to the presentapplication can attenuate the acoustic energy in an outlet stream uponthe discharging of a gas flow from a screw tooth slot primitive volume,thereby forming the muffle structure of the rotor seat for the screwcompressor. When the unit operates with different loads, the mufflestructure can attenuate the exhaust acoustic pulsation. Furthermore,since the blind holes are side branch holes and the gas flow can flow bythe side of the opening of the blind holes rather than flow into theblind holes, a measurable pressure drop may not be caused. Thus, theadditional loss of the outlet pressure can be ignored.

One advantage of the present application is a muffle structure with astructure which is simple, compact and very reliable.

Another advantage of the present application is that no additionalstructure is needed for noise control, which provides for a reducedcost.

Other features and advantages of the present invention will be apparentfrom the following, more detailed description of the preferredembodiments, taken in conjunction with the accompanying drawings whichillustrate, by way of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exemplary embodiment for a heating, ventilation and airconditioning system.

FIG. 2 shows an isometric view of an exemplary vapor compression system.

FIGS. 3 and 4 schematically show exemplary embodiments of a vaporcompression system.

FIG. 5 schematically shows an exemplary embodiment of a structure of arotor seat for screw compressor.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 shows an exemplary environment for a heating, ventilation and airconditioning (HVAC) system 10 in a building 12 for a typical commercialsetting. System 10 can include a vapor compression system 14 that cansupply a chilled liquid which may be used to cool building 12. System 10can include a boiler 16 to supply heated liquid that may be used to heatbuilding 12, and an air distribution system which circulates air throughbuilding 12. The air distribution system can also include an air returnduct 18, an air supply duct 20 and an air handler 22. Air handler 22 caninclude a heat exchanger that is connected to boiler 16 and vaporcompression system 14 by conduits 24. The heat exchanger in air handler22 may receive either heated liquid from boiler 16 or chilled liquidfrom vapor compression system 14, depending on the mode of operation ofsystem 10. System 10 is shown with a separate air handler on each floorof building 12, but it is appreciated that the components may be sharedbetween or among floors.

FIGS. 2 and 3 show an exemplary vapor compression system 14 that can beused in HVAC system 10. Vapor compression system 14 can circulate arefrigerant through a circuit starting with compressor 32 and includinga condenser 34, expansion valve(s) or device(s) 36, and an evaporator orliquid chiller 38. Vapor compression system 14 can also include acontrol panel 40 that can include an analog to digital (A/D) converter42, a microprocessor 44, a non-volatile memory 46, and an interfaceboard 48. Some examples of fluids that may be used as refrigerants invapor compression system 14 are hydrofluorocarbon (HFC) basedrefrigerants, for example, R-410A, R-407, R-134a, hydrofluoro olefin(HFO), “natural” refrigerants like ammonia (NH₃), R-717, carbon dioxide(CO₂), R-744, or hydrocarbon based refrigerants, water vapor or anyother suitable type of refrigerant. In an exemplary embodiment, vaporcompression system 14 may use one or more of each of variable speeddrives (VSDs) 52, motors 50, compressors 32, condensers 34, expansionvalves 36 and/or evaporators 38.

Motor 50 used with compressor 32 can be powered by a variable speeddrive (VSD) 52 or can be powered directly from an alternating current(AC) or direct current (DC) power source. VSD 52, if used, receives ACpower having a particular fixed line voltage and fixed line frequencyfrom the AC power source and provides power having a variable voltageand frequency to motor 50. Motor 50 can include any type of electricmotor that can be powered by a VSD or directly from an AC or DC powersource. Motor 50 can be any other suitable motor type, for example, aswitched reluctance motor, an induction motor, or an electronicallycommutated permanent magnet motor. In an alternate exemplary embodiment,other drive mechanisms such as steam or gas turbines or engines andassociated components can be used to drive compressor 32.

Compressor 32 compresses a refrigerant vapor and delivers the vapor tocondenser 34 through a discharge passage. Compressor 32 can be a screwcompressor in one exemplary embodiment. The refrigerant vapor deliveredby compressor 32 to condenser 34 transfers heat to a fluid, for example,water or air. The refrigerant vapor condenses to a refrigerant liquid incondenser 34 as a result of the heat transfer with the fluid. The liquidrefrigerant from condenser 34 flows through expansion device 36 toevaporator 38. In the exemplary embodiment shown in FIG. 3, condenser 34is water cooled and includes a tube bundle 54 connected to a coolingtower 56.

The liquid refrigerant delivered to evaporator 38 absorbs heat fromanother fluid, which may or may not be the same type of fluid used forcondenser 34, and undergoes a phase change to a refrigerant vapor. Inthe exemplary embodiment shown in FIG. 3, evaporator 38 includes a tubebundle having a supply line 60S and a return line 60R connected to acooling load 62. A process fluid, for example, water, ethylene glycol,calcium chloride brine, sodium chloride brine, or any other suitableliquid, enters evaporator 38 via return line 60R and exits evaporator 38via supply line 60S. Evaporator 38 chills the temperature of the processfluid in the tubes. The tube bundle in evaporator 38 can include aplurality of tubes and a plurality of tube bundles. The vaporrefrigerant exits evaporator 38 and returns to compressor 32 by asuction line to complete the cycle.

FIG. 4, which is similar to FIG. 3, shows the vapor compression system14 with an intermediate circuit 64 incorporated between condenser 34 andexpansion device 36. Intermediate circuit 64 has an inlet line 68 thatcan be either connected directly to or can be in fluid communicationwith condenser 34. As shown, inlet line 68 includes an expansion device66 positioned upstream of an intermediate vessel 70. Intermediate vessel70 can be a flash tank, also referred to as a flash intercooler, in anexemplary embodiment. In an alternate exemplary embodiment, intermediatevessel 70 can be configured as a heat exchanger or a “surfaceeconomizer.” In the configuration shown in FIG. 4, i.e., theintermediate vessel 70 is used as a flash tank, a first expansion device66 operates to lower the pressure of the liquid received from condenser34. During the expansion process, a portion of the liquid vaporizes.Intermediate vessel 70 may be used to separate the vapor from the liquidreceived from first expansion device 66 and may also permit furtherexpansion of the liquid. The vapor may be drawn by compressor 32 fromintermediate vessel 70 through a line 74 to the suction inlet, a port ata pressure intermediate between suction and discharge or an intermediatestage of compression. The liquid that collects in the intermediatevessel 70 is at a lower enthalpy from the expansion process. The liquidfrom intermediate vessel 70 flows in line 72 through a second expansiondevice 36 to evaporator 38.

In an exemplary embodiment, compressor 32 can include a compressorhousing that contains the working parts of compressor 32. Vapor fromevaporator 38 can be directed to an intake passage of compressor 32.Compressor 32 compresses the vapor with a compression mechanism anddelivers the compressed vapor to condenser 34 through a dischargepassage. Motor 50 may be connected to the compression mechanism ofcompressor 32 by a drive shaft.

Vapor flows from the intake passage of compressor 32 and enters acompression pocket of the compression mechanism. The compression pocketis reduced in size by the operation of the compression mechanism tocompress the vapor. The compressed vapor can be discharged into thedischarge passage. For example, for a screw compressor, the compressionpocket is defined between the surfaces of the rotors of the compressor.As the rotors of the compressor engage one another, the compressionpockets between the rotors of the compressor, also referred to as lobes,are reduced in size and are axially displaced to a discharge side of thecompressor.

An exemplary embodiment of a rotor seat for a screw compressor is shownin FIG. 5. As shown in FIG. 5, a rotor seat 100 for a screw compressorincludes: a seat body 104, a radial exhaust port 101 arranged, locatedor positioned in the seat body 104, and a female rotor hole 102 a and amale rotor hole 102 b for receiving a female rotor and a male rotor ofthe screw compressor, respectively. A plurality of axial blind holes 103having certain or predetermined diameters and/or certain orpredetermined depths can be arranged, located or positioned on a surfacewhere the radial exhaust port 101 is located or discharges. In anexemplary embodiment, an axis of each blind hole 103 can be the normalline, at the blind hole 103, of the surface where the radial exhaustport 101 is located.

In another exemplary embodiment, the depths of the blind holes 103 canbe in the range of ¼λ±15% of an interested sound frequency, e.g., asound frequency to be attenuated, or an odd multiple of ¼λ±15% of theinterested sound frequency, where λ is the wavelength of the interestedsound frequency. For example, if the interested sound frequency is 750Hz, and the sound speed is 150 m/s, the values of the depths of theblind holes 103 can be in the range of 50 mm±15% or an odd multiple of¼λ±15% (for example, 150 mm±15%).

In a further exemplary embodiment, the diameters D of the blind holes103 can be defined by D≦0.586×c/f (where f is the interested soundfrequency, and c is the sound speed in a medium).

The blind holes 103 may be distributed in a uniform or non-uniformmanner on the surface where the radial exhaust port 101 is located, andthe quantity of the blind holes 103 can be at least two.

One exemplary embodiment provides a screw compressor with the mufflestructure or muffler. The screw compressor can include a suction port,an exhaust port, an operation cavity in communication with the suctionport and the exhaust port, and female and male rotors arranged, locatedor positioned inside the operation cavity. The screw compressor canfurther include the rotor seat 100 as shown in FIG. 5. In other words,the rotor seat 100 can include a plurality of axial blind holes 103having certain or preselected diameters and certain or preselecteddepths located or positioned on the surface where the radial exhaustport 101 of the rotor seat 100 is located, to serve as the mufflestructure. The rotor seat 100 can be for receiving the female rotor andthe male rotor.

The muffle structure formed by the blind holes 103 can attenuate theacoustic energy in an outlet stream upon the discharging of a gas flowfrom a screw tooth slot primitive volume, thereby forming the mufflestructure of the rotor seat 101 for the screw compressor. When the unitoperates with different loads, the muffle structure can always attenuatethe exhaust acoustic pulsation. Furthermore, since the blind holes 103are side branch holes and the gas flow can flow by the side of theopening of the blind holes 103 rather than flow into the blind holes103, a measurable pressure fall or pressure drop may not be caused.Thus, the additional loss of the outlet pressure can be ignored. Inaddition, the muffle structure has a structure which is simple, compactand very reliable, and no additional structure is needed, which will notbring additional costs.

It is important to note that the construction and arrangement of thepresent application as shown in the various exemplary embodiments isillustrative only. Although only a few embodiments have been describedin detail in this application, those who review this application willreadily appreciate that many modifications are possible (e.g.,variations in sizes, dimensions, structures, shapes and proportions ofthe various elements, values of parameters (e.g., temperatures,pressures, etc.), mounting arrangements, use of materials, colors,orientations, etc.) without materially departing from the novelteachings and advantages of the subject matter described in theapplication. For example, elements shown as integrally formed may beconstructed of multiple parts or elements, the position of elements maybe reversed or otherwise varied, and the nature or number of discreteelements or positions may be altered or varied. Accordingly, all suchmodifications are intended to be included within the scope of thepresent application. The order or sequence of any process or methodsteps may be varied or re-sequenced according to alternativeembodiments. In the claims, any means-plus-function clause is intendedto cover the structures described herein as performing the recitedfunction and not only structural equivalents but also equivalentstructures. Other substitutions, modifications, changes and omissionsmay be made in the design, operating conditions and arrangement of theexemplary embodiments without departing from the scope of the presentapplication. Accordingly, the present application is not limited to aparticular embodiment, but extends to various modifications thatnevertheless fall within the scope of the appended claims.

Furthermore, in an effort to provide a concise description of theexemplary embodiments, all features of an actual implementation may nothave been described (i.e., those unrelated to the presently contemplatedbest mode of carrying out the invention, or those unrelated to enablingthe invention). It should be appreciated that in the development of anysuch actual implementation, as in any engineering or design project,numerous implementation-specific decisions may be made. Such adevelopment effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure, without undue experimentation.

What is claimed is:
 1. A rotor seat for a screw compressor with a mufflestructure, the rotor seat comprising: a seat body; a radial exhaust portarranged at the seat body; a female rotor hole and a male rotor hole;and a plurality of axial blind holes arranged on an arc surface wherethe radial exhaust port is located.
 2. The rotor seat according to claim1, wherein the axis of a blind hole of the plurality of blind holes isthe normal line, at the blind hole, of the arc surface where the radialexhaust port is located.
 3. The rotor seat according to claim 2, whereinthe depths of the plurality of blind holes are in the range of ¼λ±15% ofan interested sound frequency or an odd multiple of ¼λ±15% of theinterested sound frequency, and λ is a wavelength of the interestedsound frequency.
 4. The rotor seat according to claim 2, wherein thediameters D of the plurality of blind holes are less than or equal to0.586×c/f, where f is an interested sound frequency, and c is a soundspeed in a medium.
 5. The rotor seat according to claim 1, wherein thedepths of the plurality of blind holes are in the range of ¼λ±15% of aninterested sound frequency or an odd multiple of ¼λ±15% of theinterested sound frequency, and λ is a wavelength of the interestedsound frequency.
 6. The rotor seat according to claim 5, wherein thediameters D of the plurality of blind holes are less than or equal to0.586×c/f, where f is an interested sound frequency, and c is a soundspeed in a medium.
 7. The rotor seat according to claim 1, wherein thediameters D of the plurality of blind holes are less than or equal to0.586×c/f, where f is an interested sound frequency, and c is a soundspeed in a medium.
 8. The rotor seat according to claim 7, wherein thedepths of the plurality of blind holes are in the range of ¼λ±15% of aninterested sound frequency or an odd multiple of ¼λ±15% of theinterested sound frequency, and λ is a wavelength of the interestedsound frequency.
 9. The rotor seat according to claim 1, wherein theplurality of blind holes are distributed in one of a uniform ornon-uniform manner on the arc surface where the radial exhaust port islocated.
 10. The rotor seat according to claim 1, wherein the pluralityof the blind holes is at least two blind holes.
 11. A screw compressorwith a muffle structure, the screw compressor comprising: a suctionport; an exhaust port; an operation cavity in communication with thesuction port and the exhaust port; female and male rotors arrangedinside the operation cavity; and a rotor seat to receive the female andmale rotors, the rotor seat comprising: a seat body; a radial exhaustport arranged at the seat body; a female rotor hole and a male rotorhole; and a plurality of axial blind holes arranged on a surface wherethe radial exhaust port is located.
 12. The screw compressor accordingto claim 11, wherein the axis of a blind hole of the plurality of blindholes is the normal line, at the blind hole, of the surface where theradial exhaust port is located.
 13. The screw compressor according toclaim 12, wherein the depths of the plurality of blind holes are in therange of ¼λ±15% of an interested sound frequency or an odd multiple of¼λ±15% of the interested sound frequency, and λ is a wavelength of theinterested sound frequency.
 14. The screw compressor according to claim12, wherein the diameters D of the plurality of blind holes are lessthan or equal to 0.586×c/f, where f is an interested sound frequency,and c is a sound speed in a medium.
 15. The screw compressor accordingto claim 11, wherein the depths of the plurality of blind holes are inthe range of ¼λ±15% of an interested sound frequency or an odd multipleof ¼λ±15% of the interested sound frequency, and λ is a wavelength ofthe interested sound frequency.
 16. The screw compressor according toclaim 15, wherein the diameters D of the plurality of blind holes areless than or equal to 0.586×c/f, where f is an interested soundfrequency, and c is a sound speed in a medium.
 17. The screw compressoraccording to claim 11, wherein the diameters D of the plurality of blindholes are less than or equal to 0.586×c/f, where f is an interestedsound frequency, and c is a sound speed in a medium.
 18. The screwcompressor according to claim 17, wherein the depths of the plurality ofblind holes are in the range of ¼λ×15% of an interested sound frequencyor an odd multiple of ¼λ±15% of the interested sound frequency, and λ isa wavelength of the interested sound frequency.
 19. The screw compressoraccording to claim 11, wherein the plurality of blind holes aredistributed in one of a uniform or non-uniform manner on the surfacewhere the radial exhaust port is located.
 20. The screw compressoraccording to claim 11, wherein the plurality of the blind holes is atleast two blind holes.